Method and device for determining the load condition of an exhaust gas particulate filter

ABSTRACT

The disclosure relates to a method and a device for determining the load condition of an exhaust gas particulate filter that is arranged in an exhaust gas path of an internal combustion engine that is charged by an exhaust gas turbocharger. The behavior of a charging pressure controller or the charging pressure of the exhaust gas turbocharger is analyzed to determine the load condition of the exhaust gas particulate filter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International application No.PCT/EP2016/058198, filed Apr. 14, 2016, which claims priority to Germanpatent application No. 10 2015 211 151.2, filed Jun. 17, 2015. Thedisclosures of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The disclosure relates to a method and a device for determining the loadcondition of an exhaust gas particulate filter.

BACKGROUND

Modern motor vehicles having diesel engines are generally fitted with anexhaust gas particulate filter system for treating exhaust gas in orderto be able to comply with legal requirements regarding particulateemissions. However, even in the case of petrol engines legalrequirements regarding exhaust gas particulate emissions are expected tobecome stricter with the result that in the future vehicles having apetrol engine may also have to be fitted with an exhaust gas particulatefilter.

Exhaust gas particulate filter systems filter out the soot particulatesthat are produced during engine combustion. Since the soot particulatestorage capability of an exhaust gas particulate filter is limited, itis necessary to regenerate the exhaust gas particulate filter in thecase of a correspondingly high load. During this regeneration procedure,soot particulates that have collected in the filter are burned with theresult that new soot particulates can be collected in the regeneratedexhaust gas particulate filter.

An exhaust gas particulate filter is regenerated typically at a hightemperature that either occurs during the practical driving operation oris generated on demand by a corresponding adjustment of engineparameters. Such an artificial regeneration procedure is activated ingeneral in dependence on the load condition of the exhaust gasparticulate filter, the load condition being determined typically withreference to the exhaust gas backpressure that increases with anincreasing particulate load.

If the exhaust gas backpressure or the differential pressure across theparticulate filter exceeds a predetermined threshold value during theoperation of the engine, the exhaust gas temperature is increased, by acorresponding adjustment of the engine parameters, to above thetemperature at which the soot particulates are combusted, consideringfurther parameters such as, by way of example, the operating temperatureand the engine rotational speed.

Determining an increase in the exhaust gas backpressure using exhaustgas pressure sensors that are installed in the exhaust gas systemupstream and, where appropriate, also downstream of the exhaust gasparticulate filter, or using differential pressure sensors that measurea pressure increase across the filter system is already known.

One disadvantage of this approach resides in the fact that the abovementioned sensors are heavily stressed owing to the high exhaust gastemperature that is associated with the installation position and thecontamination caused by the exhaust gas. This results, on the one hand,in high costs for suitable sensors and, on the other hand, in anincreased susceptibility to a failure of the sensors.

A known method and a device for controlling the regeneration procedureof a particulate filter may be used in an internal combustion enginethat includes an intake air compressor system and is coupled in afluidically to an exhaust gas post-treatment system that includes aparticulate filter. The method includes using engine operating points todetermine a steady-state generation rate of the soot that is exiting theengine, setting the steady-state generation rate of the soot that isexiting the engine as a reaction to a transient change in a chargingpressure of the intake air compressor system and controlling theregeneration procedure of the particulate filter as a reaction to theset steady-state generation rate of the soot that is exiting the engine.The controlling the regeneration of the particulate filter as a reactionto the set generation rate of the soot that is exiting the enginecomprises chronologically integrating the set chronologicallysteady-state generation rate of the soot that is exiting the engine andordering regeneration of the particulate filter if the chronologicallyintegrated set generation rate of the soot that is exiting the engineexceeds a predetermined threshold value.

Another known method includes performing a plausibility check on adetermined differential pressure value across a particulate filter. Thisplausibility evaluation is performed using a first measuring unit fordetermining the differential pressure value and a second measuring unitthat determines a charging pressure of the internal combustion engine. Acharging pressure value of the internal combustion engine is assigned toeach differential pressure value. The two characteristic values arestored in a characteristic diagram storage device. An erroneousdifferential pressure value is identified if the measured differentialpressure value is outside a predeterminable upper and lower thresholdvalue range for the differential pressure value that is stored andallocated to the respective determined charging pressure of the internalcombustion engine.

SUMMARY

The disclosure provides a method for determining the load condition ofan exhaust gas particulate filter that does not require exhaust gaspressure sensors and nevertheless reliably determines the point in timeat which the regeneration procedure of the exhaust gas particulatefilter is due.

The method is provided for determining the load condition of an exhaustgas particulate filter that is arranged in the exhaust gas path of aninternal combustion engine that is charged by a turbocharger. Thebehavior of a charging pressure controller of the exhaust gasturbocharger is analyzed in the method to determine the load conditionof the exhaust gas particulate filter.

Executing a procedure of indirectly determining the load condition inthis manner, makes it unnecessary to measure the exhaust gas pressureupstream and downstream of the particulate filter using exhaust gaspressure sensors. A differential pressure sensor is not required either.Consequently, problems that occur in the case of known methods owing tothe arrangement of such sensors in the hot exhaust tract of an internalcombustion engine are avoided.

One aspect of the disclosure provides a method for determining the loadcondition of an exhaust gas particulate filter that is arranged in theexhaust gas path of an internal combustion engine. The internalcombustion engine is charged by an exhaust gas turbocharger. Thebehavior of a charging pressure controller or the charging pressure ofthe exhaust gas turbocharger is analyzed to determine the load conditionof the exhaust gas particulate filter.

Implementations of the disclosure may include one or more of thefollowing optional features. In some implementations, a long-termobservation of the behavior of the charging pressure controller or thecharging pressure of the exhaust gas turbocharger is performed todetermine the load condition of the exhaust gas particulate filter. Insome examples, the charging pressure controller provides control signalsfor the exhaust gas turbocharger and an evaluation of these controlsignals is performed in order to determine adaptation values for a pilotcontrol procedure of the exhaust gas turbocharger, and a check isperformed as to whether a change in the adaptation values occur in thelong term.

In some implementations, a check is performed as to whether acharacteristic change in the control signals that are output by thecharging pressure controller occurs in the long term. A check may beperformed as to whether characteristic deviations occur between acharging pressure desired value and a charging pressure actual value inthe long term. In some examples, a point in time directly after theexhaust gas particulate filter has been regenerated is selected as astarting point in time for the analysis of the behavior of the chargingpressure controller.

Another aspect of the disclosure provides a device for determining theload condition of an exhaust gas particulate filter that is arranged inthe exhaust gas path of an internal combustion engine that is charged byan exhaust gas turbocharger. The device includes a control unitconfigured to perform the method described above.

The details of one or more implementations of the disclosure are setforth in the accompanying drawings and the description below. Otheraspects, features, and advantages will be apparent from the descriptionand drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a block diagram of a device for determining the loadof an exhaust gas particulate filter.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

FIG. 1 shows a device for determining the load of an exhaust gasparticulate filter. The device includes an internal combustion engine 1,an exhaust gas turbocharger 2 that includes a turbine 3 and a compressor5, an exhaust gas particulate filter 6, a control unit 7, an operatingprogram storage device 8 and a data storage device 9. The turbine 3 issupplied with the hot exhaust gas of the internal combustion engine 1and uses said hot exhaust gas to drive a turbine wheel. The turbinewheel is connected in a non-rotatable manner to a shaft 4. The shaft 4is in turn connected in a non-rotatable manner to a compressor wheelthat is arranged in the compressor 5 with the result that rotations ofthe turbine wheel are transferred to the compressor wheel. The fresh airthat is supplied to the compressor is compressed by the rotation of thecompressor wheel. The compressed fresh air is supplied to the internalcombustion engine 1 and is used to increase the power of the engine.

Furthermore, the illustrated device includes a control unit 7, forexample, the control device of the motor vehicle. The control unit 7 isconnected to an operating program storage device 8 in which theoperating program of the control unit is stored. Furthermore, thecontrol unit 7 is connected to a data storage device 9 in which data isstored that corresponds inter alia to characteristic diagrams that arerequired by the control unit 7 during operation of the motor vehicle.

The control unit 7 includes a charging pressure controller 7 a that isused for controlling the charging pressure of the exhaust gasturbocharger 2 during operation of the exhaust gas turbocharger 2.

The control unit 7 determines and outputs, during operation of the motorvehicle, control signals s1, s2 and s3 that depend on the sensor signalsse1 that are supplied to the control unit 7 using the operating programand with the aid of the data that is stored in the storage device 9. Thecontrol signals s1 are used to control the internal combustion engine 1,the control signal s2 for controlling the actuators of the turbine 3 andthe control signal s3 for controlling the actuators of the compressor 5.A wastegate valve or a variable turbine geometry is associated with theactuators of the turbine 3, and the opening state of the valves isaltered on demand by the control signal s2. A bypass valve is associatedwith the actuators of the compressor 5 and compressed air is suppliedvia the bypass valve back to the input of the compressor 5 on demand.The opening state of this bypass valve is set by the control signal s3.

The abovementioned control signals se1 include inter alia the outputsignal of an accelerator pedal sensor that indicates an actuation of theaccelerator pedal, the output signal of one or multiple temperaturesensors that each provides information regarding a temperature that ismeasured at a predetermined location on the exhaust gas turbocharger,and the output signal of a pressure sensor that provides informationregarding the pressure of the compressed air that is present at theoutput of the compressor.

Controlling the actuators of the exhaust gas turbocharger 2 is interalia dependent on the exhaust gas backpressure since the output power ofthe turbine 3 is determined from the drop in the pressure across theturbine. This drop in the pressure across the turbine is defined by theexhaust gas backpressure downstream of the outlet valve or outlet valvesof the internal combustion engine and by the exhaust gas backpressuredownstream of the turbine, i.e., the exhaust gas backpressure upstreamof the particulate filter 6. In the case of an identical operating pointof the internal combustion engine, an increase in the exhaust gasbackpressure upstream of the particulate filter 6 as a result of anincreased flow resistance in the particulate filter 6 therefore leads toa reduced pressure drop across the turbine. Consequently, the power thatis output by the turbine is less than the power that is determined bythe control unit 7 using the stored characteristic diagrams, since thestored engine characteristic diagram was created based on the drop inpressure across the turbine in the case of an unloaded exhaust gasparticulate filter. During operation of the internal combustion enginethe desired charging pressure that is requested by the control unit forthe engine operating point that is to be set is not entirely realizedwith a pilot control procedure that relates to the stored enginecharacteristic diagram. Consequently, there is a difference between thedesired charging pressure and the actual charging pressure, thedifference being compensated by the charging pressure controller 7 athat is present in the control unit. This leads to a controllerdeviation that is also dependent upon the load condition of the exhaustgas particulate filter 6.

The behavior of the charging pressure controller 7 a may therefore beused to determine the load condition of the exhaust gas particulatefilter 6. Consequently, the point in time of a required regenerationprocedure of the exhaust gas particulate filter may be determined usingan analysis of the behavior of the charging pressure controller 7 a.

There are different possibilities for this analysis of the behavior ofthe charging pressure controller 7 a. In general, the procedure ofloading the exhaust gas particulate filter to the point in time at whichit is necessary to regenerate the exhaust gas particulate filter takes arelatively longer time. Consequently, it is necessary to performlong-term observation of the behavior of the charging pressurecontroller 7 a and therefore also of the pilot control requirement ofthe exhaust gas turbocharger 2. An analysis of the required adaptationsof the pilot control procedure of the exhaust gas turbocharger issuitable for such long-term observation. Long-term observation ofcharging pressure overshoots and charging pressure undershoots is alsosuitable.

A point in time directly after the execution of a regeneration procedureis selected in an advantageous manner as a starting point in time for along-term observation of this type. At this point in time the abovementioned adaptation values for the pilot control of the turbochargerare reset. Starting from this point in time, new long-term observationof the adaptation values for the preset control procedure of the exhaustgas turbocharger is to be performed.

Alternatively or in addition thereto, it is also possible to perform acheck as to whether characteristic changes of the control signals thatare output by the charging pressure controller occur in the long term.Furthermore, alternatively or in addition thereto it is possible toperform a check as to whether characteristic deviations occur betweenthe charging pressure desired value and the charging pressure actualvalue in the long term.

All the above-mentioned checking procedures are performed in dependenceon changes that occur in the exhaust gas backpressure.

It follows that the present invention provides a method and a device inwhich a conclusion is drawn that it is necessary to perform modifiedpilot control of the exhaust gas turbocharger in response to a change inthe drop in pressure across the turbine as a result of an increase inthe exhaust gas backpressure in the exhaust gas particulate filter, theincrease being caused by increased loading of the exhaust gasparticulate filter.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Accordingly, otherimplementations are within the scope of the following claims.

What is claimed is:
 1. A method for determining a load condition of anexhaust gas particulate filter arranged in an exhaust gas path of aninternal combustion engine, the internal combustion engine is charged byan exhaust gas turbocharger, the method comprising: analyzing a behaviorof a charging pressure controller or the charging pressure of theexhaust gas turbocharger; and determining the load condition of theexhaust gas particulate filter based on the analyzed behavior of thecharging pressure controller or the charging pressure of the exhaust gasturbocharger.
 2. The method of claim 1, further comprising: performing along-term observation of the behavior of the charging pressurecontroller or the charging pressure of the exhaust gas turbocharger; anddetermining the load condition of the exhaust gas particulate filterbased on the long-term observation.
 3. The method of claim 1, furthercomprising: evaluating control signals provided by the charging pressurecontroller; determining adaptation values for a pilot control procedureof the exhaust gas turbocharger based on the evaluated control signal;and performing a check for determining whether a change in theadaptation values occurs in the long term.
 4. The method of claim 3,further comprising performing a check for determining whether acharacteristic change in the control signals that are output by thecharging pressure controller occurs in the long term.
 5. The method ofclaim 1, further comprising performing a check for determining whethercharacteristic deviations occur between a charging pressure desiredvalue and a charging pressure actual value in the long term.
 6. Themethod of claim 1, further comprising selecting a point in time directlyafter the exhaust gas particulate filter has been regenerated as astarting point in time for the analysis of the behavior of the chargingpressure controller.
 7. A device for determining a load condition of anexhaust gas particulate filter that is arranged in an exhaust gas pathof an internal combustion engine that is charged by an exhaust gasturbocharger, the device comprises a control unit configured to executea method, the method comprising: analyzing a behavior of a chargingpressure controller or the charging pressure of the exhaust gasturbocharger; and determining the load condition of the exhaust gasparticulate filter based on the analyzed behavior of the chargingpressure controller or the charging pressure of the exhaust gasturbocharger.
 8. The device of claim 7, wherein the method furthercomprises: performing a long-term observation of the behavior of thecharging pressure controller or the charging pressure of the exhaust gasturbocharger; and determining the load condition of the exhaust gasparticulate filter based on the long-term observation.
 9. The device ofclaim 7, wherein the method further comprises: evaluating controlsignals provided by the charging pressure controller; determiningadaptation values for a pilot control procedure of the exhaust gasturbocharger based on the evaluated control signal; and performing acheck for determining whether a change in the adaptation values occursin the long term.
 10. The device of claim 9, wherein the method furthercomprises performing a check for determining whether a characteristicchange in the control signals that are output by the charging pressurecontroller occurs in the long term.
 11. The device of claim 7, whereinthe method further comprises performing a check for determining whethercharacteristic deviations occur between a charging pressure desiredvalue and a charging pressure actual value in the long term.
 12. Thedevice of claim 7, further comprising selecting a point in time directlyafter the exhaust gas particulate filter has been regenerated as astarting point in time for the analysis of the behavior of the chargingpressure controller.